docs: def counter(group, counter, amount=1, err=None):
      """Output a counter update that is displayed in the Hadoop web interface
  
      Counters are useful for quickly identifying the number of times an error
      occurred, current progress, or coarse statistics.
  
      :param group: Counter group
      :param counter: Counter name
      :param amount: Value to add (default 1)
      :param err: Func that outputs a string, if None then sys.stderr.write is used (default None)
      """
      if not err:
          err = _err
      err("reporter:counter:%s,%s,%s\n" % (group, counter, str(amount)))